Research
CHARACTERIZING RESPONSES TO STONY CORAL TISSUE LOSS DISEASE AND INTERVENTION STRATEGIES
A newly-described disease, stony coral tissue loss disease (SCTLD), has been affecting coral reefs in southeast Florida since 2014, and has now spread to other reefs in the Caribbean. This disease affects at least 22 species of scleractinian corals and causes rapid colony mortality through liquefactive necrosis. We currently know very little about SCTLD, including the pathogen, mode of infection, individual susceptibility, and potential resistance in coral populations.
As part of a multi-faceted collaborative effort to better understand this disease and its effects on reef populations in the Florida's Coral Reef, we are testing disease intervention strategies on fate-tracked coral colonies. To assess intervention success and disease progression rates, we are profiling whole-transcriptome gene expression with RNA-Seq, and have optimized a 3D modeling protocol. Established survey methods can only estimate percent mortality over time, whereas we can quantitatively measure surface areas of live coral tissue, infected tissue, and tissue loss through time. We are evaluating this method with an artificial coral colony of known dimensions and with fate-tracked coral colonies in south FL.
https://www.frontiersin.org/articles/10.3389/fmars.2021.815698/full
https://www.frontiersin.org/articles/10.3389/fmars.2021.682163/full
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0252593
A newly-described disease, stony coral tissue loss disease (SCTLD), has been affecting coral reefs in southeast Florida since 2014, and has now spread to other reefs in the Caribbean. This disease affects at least 22 species of scleractinian corals and causes rapid colony mortality through liquefactive necrosis. We currently know very little about SCTLD, including the pathogen, mode of infection, individual susceptibility, and potential resistance in coral populations.
As part of a multi-faceted collaborative effort to better understand this disease and its effects on reef populations in the Florida's Coral Reef, we are testing disease intervention strategies on fate-tracked coral colonies. To assess intervention success and disease progression rates, we are profiling whole-transcriptome gene expression with RNA-Seq, and have optimized a 3D modeling protocol. Established survey methods can only estimate percent mortality over time, whereas we can quantitatively measure surface areas of live coral tissue, infected tissue, and tissue loss through time. We are evaluating this method with an artificial coral colony of known dimensions and with fate-tracked coral colonies in south FL.
https://www.frontiersin.org/articles/10.3389/fmars.2021.815698/full
https://www.frontiersin.org/articles/10.3389/fmars.2021.682163/full
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0252593
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QUANTIFYING GENETIC CONNECTIVITY AND GENE FLOW AMONG SHALLOW AND MESOPHOTIC REEFS ACROSS THE GULF OF MEXICO
Corals can live for hundreds, if not thousands, of years, and we know very little about both the biology of coral reproduction, and the movement of larvae to new reefs (recruitment). To study even a single coral over its entire lifetime or to follow individual larvae after a spawning event is a near impossible task, so we turn to genetic techniques to answer our questions about coral populations and larval migration. Genetic markers within the genome, such as microsatellites, capture this kind of information over ecological timescales. By analyzing how coral populations differ in their combinations of genotypes, we can predict the level of gene flow, historical population sources, and migration rates using mathematical models.
We used nine microsatellite markers found within the depth-generalist coral species Montastraea cavernosa to identify how shallow and mesophotic coral populations are related across the Gulf of Mexico. This information is especially valuable to understand how reefs interact across thousands of kilometers of open ocean, and uncovers if mesophotic corals may provide larvae to their shallow counterparts.
https://link.springer.com/article/10.1007/s00338-018-1733-7
https://www.nature.com/articles/s41598-019-43479-x
https://www.frontiersin.org/articles/10.3389/fmicb.2020.00518
Corals can live for hundreds, if not thousands, of years, and we know very little about both the biology of coral reproduction, and the movement of larvae to new reefs (recruitment). To study even a single coral over its entire lifetime or to follow individual larvae after a spawning event is a near impossible task, so we turn to genetic techniques to answer our questions about coral populations and larval migration. Genetic markers within the genome, such as microsatellites, capture this kind of information over ecological timescales. By analyzing how coral populations differ in their combinations of genotypes, we can predict the level of gene flow, historical population sources, and migration rates using mathematical models.
We used nine microsatellite markers found within the depth-generalist coral species Montastraea cavernosa to identify how shallow and mesophotic coral populations are related across the Gulf of Mexico. This information is especially valuable to understand how reefs interact across thousands of kilometers of open ocean, and uncovers if mesophotic corals may provide larvae to their shallow counterparts.
https://link.springer.com/article/10.1007/s00338-018-1733-7
https://www.nature.com/articles/s41598-019-43479-x
https://www.frontiersin.org/articles/10.3389/fmicb.2020.00518
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COMBINING POPULATION GENETICS AND LARVAL BIOPHYSICAL MODELING TO SUPPORT THE EXPANSION OF A NATIONAL MARINE SANCTUARY
The northwest Gulf of Mexico is home to a diverse assemblage of shallow and mesophotic banks habitats, despite its high-latitude isolation from other reef systems in the Tropical Western Atlantic. Three of the dozens of banks along the continental shelf margin are currently protected within Flower Garden Banks National Marine Sanctuary (West FGB, East FGB, and Stetson Bank). Some of the other downstream mesophotic banks are afforded limited protection from fishing and offshore oil activities (Bright, Geyer, and McGrail Banks).
A recent proposal by the FGBNMS Sanctuary Advisory Council is seeking to expand the NMS boundaries to include 15 additional mesophotic banks. We addressed whether coral populations across some of the banks outside the current NMS boundaries may be acting as source populations for FGB, and whether a combined management approach is appropriate. The genetic data from this research were also compared to a biophysical model estimating larval migration within the northwest Gulf. Both projects will be useful for future management strategies to protect these high-latitude coral reef systems.
www.frontiersin.org/articles/10.3389/fmars.2018.00152
www.frontiersin.org/articles/10.3389/fmars.2018.00174
The northwest Gulf of Mexico is home to a diverse assemblage of shallow and mesophotic banks habitats, despite its high-latitude isolation from other reef systems in the Tropical Western Atlantic. Three of the dozens of banks along the continental shelf margin are currently protected within Flower Garden Banks National Marine Sanctuary (West FGB, East FGB, and Stetson Bank). Some of the other downstream mesophotic banks are afforded limited protection from fishing and offshore oil activities (Bright, Geyer, and McGrail Banks).
A recent proposal by the FGBNMS Sanctuary Advisory Council is seeking to expand the NMS boundaries to include 15 additional mesophotic banks. We addressed whether coral populations across some of the banks outside the current NMS boundaries may be acting as source populations for FGB, and whether a combined management approach is appropriate. The genetic data from this research were also compared to a biophysical model estimating larval migration within the northwest Gulf. Both projects will be useful for future management strategies to protect these high-latitude coral reef systems.
www.frontiersin.org/articles/10.3389/fmars.2018.00152
www.frontiersin.org/articles/10.3389/fmars.2018.00174
Map Credit: Sanctuary Advisory Council, FGBNMS Expansion Preferred Alternative 3
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ASSESSING SIMILARITIES AMONG SHALLOW AND MESOPHOTIC CONSPECIFICS USING CORALLITE MORPHOMETRICS
In addition to knowledge about genetic connectivity of corals across depths, we must understand how shallow and mesophotic corals adapt to their different environments. Light limitation at mesophotic depths results in a shift in growth strategies from mounding to plating morphologies and reduction in corallite (the skeleton supporting each polyp) size as a way to maximize light capture.
Through an examination of microstructures within corallites, we determined how overall skeletal structure differs across depth, and whether mesophotic corals exhibited any unique mechanisms to living in low-light environments. In doing so, we identified two morphotypes with different depth distributions, algal symbiont (Symbiodinaceae) densities, and chlorophyll concentrations.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0203732
In addition to knowledge about genetic connectivity of corals across depths, we must understand how shallow and mesophotic corals adapt to their different environments. Light limitation at mesophotic depths results in a shift in growth strategies from mounding to plating morphologies and reduction in corallite (the skeleton supporting each polyp) size as a way to maximize light capture.
Through an examination of microstructures within corallites, we determined how overall skeletal structure differs across depth, and whether mesophotic corals exhibited any unique mechanisms to living in low-light environments. In doing so, we identified two morphotypes with different depth distributions, algal symbiont (Symbiodinaceae) densities, and chlorophyll concentrations.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0203732
ASSESSING SIMILARITIES AMONG SHALLOW AND MESOPHOTIC CONSPECIFICS USING GENE EXPRESSION PROFILING
Before changes to skeletal structure and physiology are manifested, corals respond to changing environmental stimuli through differential expression of relatively needed or unneeded genes. Reduced sequencing costs and increasing availability of gene libraries (transcriptomes) for coral species now allow us to look at a snapshot of coral physiology. By extracting and sequencing all of the RNA within a sample, we can analyze tens of thousands of expressed genes to determine: a) how an individual is responding to the environment, and b) how individuals differ in their gene expression patterns from one another.
We used a coral-optimized tag-based RNA-Seq pipeline to sequence and map genes to the transcriptomes of the coral host, Montastraea cavernosa, and its dominant algal symbionts, Cladocopium sp. We sampled shallow and mesophotic corals across reefs within Belize, Flower Garden Banks, Pulley Ridge, and Dry Tortugas, allowing direct comparison of gene expression across depths and regions. With these information, we expect to better understand how individuals of the same species respond to a gradient of environmental factors.
https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.15495
Before changes to skeletal structure and physiology are manifested, corals respond to changing environmental stimuli through differential expression of relatively needed or unneeded genes. Reduced sequencing costs and increasing availability of gene libraries (transcriptomes) for coral species now allow us to look at a snapshot of coral physiology. By extracting and sequencing all of the RNA within a sample, we can analyze tens of thousands of expressed genes to determine: a) how an individual is responding to the environment, and b) how individuals differ in their gene expression patterns from one another.
We used a coral-optimized tag-based RNA-Seq pipeline to sequence and map genes to the transcriptomes of the coral host, Montastraea cavernosa, and its dominant algal symbionts, Cladocopium sp. We sampled shallow and mesophotic corals across reefs within Belize, Flower Garden Banks, Pulley Ridge, and Dry Tortugas, allowing direct comparison of gene expression across depths and regions. With these information, we expect to better understand how individuals of the same species respond to a gradient of environmental factors.
https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.15495
COMPARING GENOTYPIC AND ENVIRONMENTAL INFLUENCES WITH A TRANSPLANT EXPERIMENT
Nature vs nurture is a yet-unanswered concept with corals. Individuals within the same species show a high level of variability in appearance, physiology, and behavior. We do not fully understand whether corals respond to environmental gradients in predictable ways (plasticity), or whether genetic identity (genotype) confers some kind of differential response. Transplant experiments are a great way to determine the relative impacts of genotype and environment on coral responses.
We conducted a transplant experiment at West and East Flower Garden Banks from October 2015 - July 2018. In addition to tracking unmanipulated corals at shallow and mesophotic depths, some colonies were transplanted from mesophotic to shallow depth zones. Through repeated sampling of these corals, we compared the changes in gene expression through time. Analysis of gene pathways may be able to uncover trends due to respective genotypic and environmental influences.
https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.15495
Nature vs nurture is a yet-unanswered concept with corals. Individuals within the same species show a high level of variability in appearance, physiology, and behavior. We do not fully understand whether corals respond to environmental gradients in predictable ways (plasticity), or whether genetic identity (genotype) confers some kind of differential response. Transplant experiments are a great way to determine the relative impacts of genotype and environment on coral responses.
We conducted a transplant experiment at West and East Flower Garden Banks from October 2015 - July 2018. In addition to tracking unmanipulated corals at shallow and mesophotic depths, some colonies were transplanted from mesophotic to shallow depth zones. Through repeated sampling of these corals, we compared the changes in gene expression through time. Analysis of gene pathways may be able to uncover trends due to respective genotypic and environmental influences.
https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.15495
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